Athletes tend to have lower resting blood pressure because regular training reshapes the heart, blood vessels, and nervous system in ways that reduce the force needed to circulate blood. These changes are adaptive, not problematic. A trained endurance athlete may walk around with a resting heart rate in the 40s or 50s and blood pressure well below the standard 120/80 mmHg, and that’s the cardiovascular system working more efficiently, not failing.
A Bigger, Stronger Heart Pumps More Per Beat
The most fundamental change is in the heart itself. With consistent aerobic training, the left ventricle (the heart’s main pumping chamber) gradually enlarges and strengthens. This means it can push out more blood with each beat, a measurement called stroke volume. When the heart moves more blood per contraction, it doesn’t need to beat as often or as forcefully at rest to deliver oxygen throughout the body.
This remodeling has been recognized since the early 1900s, when researchers first noted that the slow heart rates of trained athletes weren’t a sign of disease but a sign of efficiency. A sedentary person’s heart might pump around 70 milliliters of blood per beat at rest, while an elite endurance athlete’s heart can pump significantly more. That extra volume per beat is what allows the heart to maintain adequate blood flow at a lower pressure and slower rate.
Blood Vessels Open Up and Resistance Drops
Blood pressure isn’t just about how hard the heart pumps. It also depends on how much resistance the blood encounters as it moves through your arteries and smaller vessels. Exercise training decreases peripheral vascular resistance, meaning the blood vessels relax and widen, offering less pushback against blood flow. Arteries become more elastic, and the network of tiny capillaries feeding muscles and organs expands. The result is a wider, more compliant highway for blood to travel through, which naturally lowers the pressure inside the system.
This is one reason endurance athletes see the most dramatic blood pressure reductions. Activities like running, cycling, and swimming repeatedly demand large volumes of blood flow to working muscles, and over months and years the vascular system physically adapts to accommodate that demand, even at rest.
The Vagus Nerve Acts as a Brake
Your autonomic nervous system has two competing branches: one that speeds things up (sympathetic, the “fight or flight” side) and one that slows things down (parasympathetic, the “rest and digest” side). The vagus nerve is the main parasympathetic highway, and athletes develop stronger vagal tone than sedentary people.
At the heart, vagal nerve fibers release a chemical signal at the node that sets heart rhythm, slowing the heartbeat and lowering blood pressure. In well-trained athletes, this vagal brake is exceptionally strong at rest. Their nervous system defaults to a calm, low-output state, only ramping up when exercise demands it. This is measurable through heart rate variability (HRV), which reflects how much beat-to-beat variation the heart displays. High HRV signals an adaptable autonomic system with strong vagal influence, and athletes consistently show higher HRV than the general population.
This vagal dominance also makes the baroreflex, the body’s built-in blood pressure sensor, more efficient. The system detects pressure changes faster and corrects them more smoothly, keeping resting blood pressure in a lower, steadier range.
More Blood Volume, Lower Pressure
Endurance training expands total blood volume, particularly the plasma (liquid) portion. This might seem counterintuitive: more fluid in the system sounds like it should raise pressure, not lower it. But the expanded volume stretches the heart chambers, allowing them to fill more completely before each contraction and eject more blood per beat through the Frank-Starling mechanism. Research from the American Physiological Society found that plasma and total blood volume were independent predictors of stroke volume in trained athletes. In other words, the extra fluid directly supports the heart’s ability to pump efficiently, which circles back to the lower heart rate and lower resting pressure.
Endurance vs. Strength Athletes
Not all athletes experience the same blood pressure changes. The low resting blood pressure most people associate with athletes is primarily an endurance sport phenomenon. Runners, cyclists, swimmers, and cross-country skiers develop the most pronounced cardiac remodeling and vascular relaxation.
Power and strength athletes tell a different story. Studies show that athletes in weightlifting, rowing, and American football have higher blood pressure levels and are more likely to have prehypertension or outright hypertension, with prevalence ranging from about 9% to as high as 26%. Heavy resistance training raises blood pressure acutely during lifts (sometimes dramatically), and the chronic adaptations differ from endurance work. The heart wall thickens to handle pressure overload rather than expanding its chamber volume, and the vascular changes that lower resistance in endurance athletes are less pronounced.
When Low Blood Pressure Becomes a Problem
For most trained athletes, low resting blood pressure is entirely benign. But there are situations where it crosses into symptomatic territory. After ultraendurance events like marathons and ultramarathons, many runners show mild hypotension with systolic readings in the 90 to 100 mmHg range. In a systematic review of ultraendurance athletes, post-race measurements showed an average systolic drop of 18 mmHg (about 14.5%) and a diastolic drop of 10 mmHg (about 13.3%) when standing compared to lying down. These changes reflect temporary cardiovascular stress from prolonged exertion, dehydration, and blood flow redistribution rather than a chronic problem.
Day to day, some athletes experience lightheadedness when standing up quickly, particularly if they’re dehydrated or have been sitting for a long time. This happens because their low baseline pressure leaves less margin before blood flow to the brain temporarily dips. It’s worth paying attention to persistent dizziness, fainting, unusual fatigue, or blurred vision, as these can signal that blood pressure is too low to maintain adequate organ perfusion. But in the absence of symptoms, a systolic reading in the low 100s or even 90s in a fit endurance athlete is the cardiovascular system doing exactly what training built it to do.
What About High Readings in Athletes?
Interestingly, some highly conditioned athletes, particularly young men, can show systolic blood pressure in the prehypertension range (120 to 139 mmHg) or even stage 1 hypertension range during an office visit. This happens precisely because their stroke volume is so large that each heartbeat generates a wide pulse pressure. In these cases, the diastolic number is usually normal, and the elevated systolic reading reflects the force of a powerful pump pushing through relaxed vessels rather than the stiff, constricted vasculature seen in true hypertension.
White coat hypertension is also common among athletes. In one study of 410 young athletes, 18 had elevated office blood pressure readings, but 88% of those turned out to have completely normal 24-hour ambulatory blood pressure when measured outside the clinic. This is why out-of-office monitoring is particularly useful for athletes whose in-clinic numbers seem high.